Method for assembling multiple-section cylinders



J. w. HAT-CH 2,897,586

Aug. 4, '1959 METHOD FOR ASSEMBLING MULTIPLESECTION CYLINDERS Filed June 13, 1955 JAMES I HATCH,

IN V EN TOR.

I A TTORNE).

Patented Aug. 4, 1959 METHOD FOR ASSEMBLING MULTIPLE-SECTION CYLINDERS James W. Hatch, Los Angeles, Calif., assignor to Monarch Engineering Corporation, Gardena, Califi, a corporation of California Application June 13, 1955, Serial No. 514,983 4 Claims. (Cl. 29 -467) This invention relates to a method for assembling cylindrical sections end-to-end to produce a unified multiple-section barrel for an oil well pump or the like, the individual sections of the barrel having conically tapered male and female ends nested together and bonded together by brazing. Such a pump for use in an oil well has a relatively long barrel, usually several feet in length, in which a reciprocating pump fits in a relatively snug manner.

The problem is to provide such a pump barel that has a precision bore throughout its length and, in addition, is made of material to withstand the corrosive effects of oil well fluids. Conventional seamless tubing is not suitable for this purpose because its bore is not of accurate uniform dimension and because too often such tubing warps out of accurate longitudinal alignment. A further serious disadvantage is that conventional seamless tubing will not withstand the corrosive effects of oil well fluids.

It has been found that a practical procedure for fabricating such a pump barrel is, first, to make up a number of barrel sections of suificiently short length for accurate machining and then to assemble the sections end-to-end to form a multiple-section barrel. The individual sections may be made of suitable corrosion-resistant material such as brass, stainless steel, Monel metal, cast iron, and the like. The problem is how to assemble such short sections to form a long pump barrel.

The heretofore prevalent solution to this problem has been to enclose a series of the accurately dimensioned short barrel sections in an overall tubular jacket. Such a jacket not only embraces the series of cylindrical sections but also places the series of sections under longitudinal compression. Thus in a typical construction, the

jacket has at least one screw-threaded end member for abutment against one end of the series of cylindrical sections. With the series of the cylindrical sections positioned end-to-end inside the jacket, an accurately dimensioned mandrel is inserted for accurate longitudinal alignment of the cylindrical sections and then the threaded end member of the jacket is tightened to place the series under longitudinal compression while the mandrel is still in place. In some instances, suitable material is introduced into the jacket to completely fill the annular space around the series of cylindrical sections thereby to insure permanent alignment of the sections. A metal or metal alloy having a low melting point may be employed for this purpose.

Certain disadvantages are inherent in this prior art use of a jacket to solve the problem of holding the short cylindrical sections in assembled positions. The addition of the jacket involves labor and material to increase the cost, and, moreover, the jacket greatly increases the outside diameter of the pump barrel.

It has been found that the necessity for such a jacket may be eliminated if the individual cylindrical sections of the pump barrel are formed with conically tapered male and female ends and these ends are nested together and bonded together by hard solder or other suitable brazing material. Two such sections with their adjacent ends nested together under longitudinal compression may be positioned inside an induction heating coil with hard solder or the like at the juncture of the two sections and the coil may then be energized to create sufficient heat to cause the brazing material to melt and enter the space between the nested section ends to bond the ends together. A new problem arises, however, in that it has been found to be exceedingly diflicult to braze together such tapered cylindrical sections in a manner that maintains accurate axial alignment of the sections. In most instances when two such sections are heated at their mating ends, stresses occur which tend to cause the two sections to bow longitudinally across their joint. The cause of such stresses is not thoroughly understood.

The present invention is based on the discovery that whatever the cause of these misaligning stresses may be, accurate coaxial alignment of the two sections may be attained by rotating the two sections concurrently about their common axis during the bonding operation with the two sections under longitudinal compression and with the two sections mounted on a suitably snug-fitting alignment mandrel. If this procedure does not actually eliminate the cause of the misaligning stresses, it achieves the same end effect by distributing or balancing the stresses around the circumference of the two cylindrical sections.

The method of the preferred practice of the invention is further characterized by the use of an alignment mandrel having a circumferential groove for positioning at the juncture of the two sections, this circumferential groove having a sharp circumferential edge. The circumferential groove is advantageous in providing an inner circumferential clearance space into which the melted brazing material may protrude and the sharp circumferential edge of the groove is advantageous in serving as means to shear off the inwardly protruding brazing material.

The apparatus employed in carrying out the process in the preferred practice of the invention is further characterized by means mounted on the mandrel for the purpose of placing the cylindrical sections thereon under longitudinal compression. For this purpose two collars are carried by the mandrel for abutment against the opposite ends of the assembled cylindrical sections and a suitable coil spring surrounding the mandrel is in abutment with one of these collars to provide the required longitudinal compressive force. A further feature of the preferred practice of the invention in this regard is the concept of providing the mandrel with longitudinally spaced peripheral recesses for selective engagement by anchoring means to position the two collars on the mandrel. The peripheral recesses may comprise diametric bores and the anchoring means may comprise suitable pins for insertion into the diametric bores.

The various features and advantages of the invention will be apparent from the following detailed description, considered with the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative:

Figure 1 is a longitudinal sectional view of the presently preferred apparatus for carrying out the method of the invention;

Figure 2 is a fragmentary sectional detail showing a portion of Figure 1 on an enlarged scale; and

Figure 3 is a transverse sectional view taken as indicated by the line 3-3 of Figure 1.

Figure 1 shows two cylindrical sections 10 and 12 adapted to be joined end-to-end as part of a pump barrel. Any number of such sections may be bonded together to make the pump barrel as long as may be desired. Each of the two cylindrical sections 10 and 12 may be made of cast iron by a centrifugal process. The cylindrical castings are annealed, rough machined, heat treated, and then the bores of the castings are honed to precision. It is contemplated that the cylindrical sections will have conical ends adapted to be nested together and bonded together by suitable brazing material such as silver solder. In Figure 1, each of the two cylindrical sections and 12 has a male conical surface at one end and a female conical surface 15 at the other end. The adjacent ends of the two sections are shown nested together in preparation for a brazing operation to bond together the tapered joint surfaces.

The apparatus for carrying out the process of the invention includes a mandrel 16 for insertion into the sections that are to be bonded together and also includes suitable means to support the assembly comprising the sections with the mandrel therein and to permit the assembly to be rotated about its longitudinal axis. In the construction shown, two upright pedestals 18 which are anchored to the floor by suitable screws 20 are provided for rotary supporting contact with the peripheries of the two sections 11 and 12. Each of the pedestals 18 may have two parallel upstanding wings 22 in which are mounted a pair of axles 24 carrying a pair of corre sponding support rollers 25. As shown in Figure 3, the support rollers 25 of each pair are spaced apart in a manner to seat the two sections 163 and 12 in a rotatable manner.

The means for rotatably supporting the mandrel assembly further includes a third standard 26 of similar construction having a pair of upstanding wings 28 for journalling a pair of axles 36. The axles 30 carry a pair of corresponding support rollers 32 which are spaced apart to rotatably seat the exposed portion of the mandrel 16. It is apparent that this arrangement of three pairs of support rollers makes it possible and relatively easy to turn the two cylindrical sections 10 and 12 and the mandrel 16 manually about the axis of the mandrel.

In the preferred practice of the invention, the mandrel 16 has a relatively wide circumferential groove 34 and it is contemplated that this groove will be positioned at the juncture of the two cylindrical sections 10 and 12 as shown in Figure 1. A feature of the preferred practice of the invention is that the side walls of the circumferential grooves 34 are undercut to provide two sharp circumferential edges 35 (Figure 2). As shown in Figure 1, the apparatus includes an induction heating coil 36 intermediate the two standards 18 in position to surround the nested ends of the two cylindrical sections 10 and 12.

It is contemplated that the mandrel 16 will be provided with suitable means to hold the two cylindrical sections 10 and 12 nested together in intimate contact with each other during the heating operation of the induction coil 36. Various means and arrangements may be provided for this purpose in various practices of the invention.

In the construction shown in Figure 1 a suitable collar 38 is slidingly mounted on the end of the mandrel 16 for abutment against one end of the series of cylindrical sections on the mandrel. Thus the collar 33 is shown in abutment with the outer end of the cylindrical section 12. Any suitable means may be utilized to releasably maintain the collar 38 is position on the mandrel 16. For example, the mandrel may be provided with a diametrical bore 40 to receive a suitable pin 42 having an angular head 44. The pin 42 serves as a stop against which the slidable collar 38 is normally backed as shown.

For abutment against the other end of the series of cylindrical sections a collar 45 is also slidingly mounted on the mandrel 16 and preferably this second collar presses against the end of the series of cylindrical sections in a yielding manner. For this purpose the collar 45 may be formed with a circumferential flange 46 for abutment by one end of a suitable compression spring 50.

In the construction shown. the other end of the compression spring 50 abuts another collar 52 that is also slidingly mounted on the mandrel 16. The collar 52 backs against a second pin 54 having an angular head 55 and this second pin is seated in a diametrical bore 56. The mandrel 16 has a series of additional diametrical bores 56a, 5612, etc., the spacing between the various bores 56 being approximately the length of one of the cylindrical sections 10 and 12.

In preparation for the mounting of the cylindrical sections 10 and 12 on the mandrel 16, the collar 38 and the corresponding backing pin 42 may be removed from the mandrel. The other two collars 46 and 52 together with the spring 50 may be loose on the mandrel, the pin 54 being removed.

The two sections 10 and 12 are placed on the mandrel 16 in the positions shown with the circumferential groove 34 of the mandrel at the region of the juncture of the two sections. The collar 38 is then placed on the mandrel and the pin 42 is inserted into the diametrical bore 40 to serve as a stop for the collar. The collar 52 is then shifted manually towards the two cylindrical sections 10 and 12 to place the spring 50 under compression and the second pin 54 is dropped into the diametrical bore 56 to serve as a stop for holding the collar 52 in the desired position. In this manner the spring 50 is placed under compression to provide the desired force for maintaining the nested ends of the two sections 10 and 12 in suitable pressure contact with each other.

The assembly comprising the mandrel 16, with the two cylindrical sections 10 and 12 under longitudinal compression thereon is inserted through the induction coil 36 to take the position shown in Figure 1. At this position of the assembly, the two cylindrical sections 10 and 12 are in rotary peripheral contact with the two pairs of support rollers 25 and the exposed portion of the mandrel 16 is in rotary peripheral contact with the pair of support rollers 32. The assembly may now be freely rotated by hand about the longitudinal axis of the mandrel.

In carrying out the preferred practice of the invention, silver solder is placed adjacent the mating surfaces of the two cylindrical sections 10 and 12 and the induction heating coil 36 is energized for approximately a minute. The coil heats the adjacent end portions of the two cylindrical sections together with the silver solder to cause the silver solder to melt. Preferably the mandrel assembly including the two cylindrical sections 10 and 12 is rotated about its axis during this heating period. In any event, it is important that the mandrel assembly including the two cylindrical sections 10 and 12 be rotated during the subsequent period in which the metal of the cylindrical sections cools and in which the silver solder hardens to form a permanent bond between the two sections. The mandrel assembly is simply rotated by hand, the rate of rotation not being critical.

In the absence of such rotation the two bonded sections tend to bow and usually the bowing deflection is upward. If the mandrel assembly is continually rotated, there is no perceptible tendency for such bowing to occur and when the silver solder hardens the two cylindrical sections 10 and 12 are permanently bonded together in accurate longitudinal alignment.

In the course of this procedure of heat-bonding the two sections together, there is a likelihood that some of the silver solder will flow through the joint to protrude inwardly from the inner circumferential wall of the two sections in the region of the circumferential groove 34 of the mandrel. When the mandrel 16 is subsequently withdrawn from the two bonded sections 10 and 12, however, one of the two sharp circumferential edges 35 of the mandrel severs the inwardly protruding silver solder to leave the bore of the two sections smooth and c ean.

In preparation for the addition of a third cylindrical section to the two bonded cylindrical sections 10 and 12, the pin 54 is removed from the diametrical bore 56 to free the collar 52 and relieve the springs 54). The other pin 42 is then withdrawn from the diametrical bore 40 and the collar 38 is removed from the man drel. The two bonded cylindrical sections and 12 are then shifted to the left as viewed in Figure 1 to make room for an additional section.

When the additional section is placed on the end of the mandrel, the collar 38 is moved into abutment therewith and the pin 42 is inserted in the diametrical bore 40 to back up the collar. The collar 52 is then moved towards the cylindrical sections on the mandrel to again place the spring 50 under the desired degree of compression and the pin 54 is dropped into the diametrical bore 56a to hold the collar 52 in the desired position. The bonding procedure is then repeated to bond the newly added sections to the cylindrical sec tion 12.

It is apparent that any number of additional cylindrical sections may be added in this manner, the pin 54 being shifted to appropriate diametrical bores 56 at each stage of the process. It can be seen that the pin 54 serves as means for holding the collar 52 at selected positions on the mandrel when desired.

Although the now preferred embodiment of the present invention has been shown and described herein, it is to be understood that the invention is not to be limited thereto, for it is susceptible to changes in form and detail within the scope of the appended claims.

I claim:

1. A method of fabricating a relatively long barrel for an oil well pump or the like, including the steps of: forming a series of relatively short cylindrical sections with mating tapered male and female ends of conical curvature; positioning two of said sections with their adjacent ends nested together; inserting a mandrel into the two sections for accurate coaxial longitudinal alignment of the sections; placing metallic bonding material at the juncture of the nested ends of the two sections; placing an induction heating coil around the nested ends of the two sections; energizing said coil for a time period sufiicient to heat said nested ends and the bonding material to cause the bonding material to melt and to penetrate the spaces between the mating surfaces of the two ends by capillary action with consequent bonding of the two sections together; and continually rotating said two sections in unison during the bonding operation thereby to equalize forces tending to bow the two sections during the bonding operation.

2. A method as set forth in claim 1 which includes the step of placing said two sections under longitudinal compression during the period the two sections are rotated.

3. A method of fabricating a relatively long barrel for an oil well pump or the like, including the steps of: forming a series of relatively short cylindrical sections with mating tapered male and female ends of conical curvature; positioning two of said sections with their adjacent ends nested together; inserting into said two sections an alignment mandrel having a circumferential groove with a relatively sharp edge and placing said groove at the mating ends of the two sections to provide an annular space inside the two sections; placing metallic bonding material at the juncture of the nested ends of the two sections; placing the nested ends of the two sections and the enclosed mandrel inside an induction heating coil; energizing said coil for a time period sufiicient to heat said nested ends and the bonding ma terial to cause the bonding material to melt and to penetrate the spaces between the mating surfaces of the nested sections and to protrude into the spaces provided by the circumferential groove of the mandrel with consequent bonding of the two sections together; rotating said two sections and the enclosed mandrel during the bonding operation thereby to equalize forces tending to misalign the nested sections; and withdrawing said mandrel after the bonding material hardens thereby to cause said sharp edge to shear away bonding material that protrudes into the inner circumference at the joint between the two sections.

4. A method of fabricating a relatively long barrel for an oil Well pump or the like, including the steps of: forming a series of relatively short cylindrical sections with mating tapered male and female ends of conical curvature; positioning at least two of said sections with their adjacent ends nested together; inserting a mandrel into the nested sections for accurate coaxial longitudinal alignment of the sections; placing metallic bonding material at each juncture of the nested ends of the sections; placing an induction heating coil around each juncture of the nested sections; and energizing said coil for a time period sufiicient to heat the nested ends and the bonding material to cause the bonding material to melt and to penetrate the spaces between the mating surfaces of the nested ends with consequent bonding of the two sections together; continually rotating the nested sections in unison during the bonding operation thereby to equalize forces tending to bow the nested sections; and adding sections to the bonded sections with repetition of the heating and rotating steps thereby to form a unified longitudinal assembly of the sections,

References Cited in the file of this patent UNITED STATES PATENTS 2,184,534 Smith Dec. 26, 1939 2,287,197 Sandberg June 23, 1942 2,287,198 Sandberg June 23, 1942 2,291,420 SWenson July 28, 1942 2,412,797 Berliner Dec. 17, 1946 2,706,234 Macy Apr. 12, 1955 

